%!PS-Adobe-2.0 EPSF-2.0
%%Title: Plaid patch -- (plaid.eps)
%%Creator: Izumi Ohzawa, izumi@pinoko.berkeley.edu
%%CreationDate: Wed Jun 11 15:09:22 PDT 1997
%%BoundingBox: 215 215 433 433
%%EndComments

% README:
% This EPS (Encapsulated PostScript) file allows you to incorporate
% a plaid patch into your documents or graphics.
% A plaid is the sum of two sinusoidal gratings of different orientations.
% The EPS file may be imported directly into drawings or DTP documents
% by any decent software.
% If your application refuses to import this file, your application is
% positively brain-dead and should be treated accordingly (like deleting it).
% On systems running Display PostScript, the grating patch will appear as WYSIWYG.
% On other systems, it will appear as a box probably with the header info
% in the first few lines of this file.
% EPS with "preview" (PICT/TIFF) is stupid, especially for computed images
% like this.
% This is in the public domain.  Use/copy/modify freely.

% ================================================================================
% Modify the following parameters to get a desired plaid patch.
% Note that contrasts for the two gratings must satisfy:
%          Cotrast1 + Contrast2 <= 1.0
% Otherwise "rangecheck error" for operator "put" will result.

% Orientation of the whole patch, i.e., orientation of (y == const) scan lines.
/Orientation 15 def	% This will rotate the whole thing together

% === Grating componet #1 --- This component may be oriented (90 deg is vertical)
/Ncycles1  5.0 def	% # of cycles in patch (fractional values OK)
/Orient1   60.0 def	% Orientation relative to that of component #2
			% Note: Orient1 != 0 or 180 (or any multiple of 180)
/Contrast1 0.4 def	% Note:  Cotrast1 + Contrast2 <= 1.0
/Phase1 0 def

% === Grating componet #2 --- Horizontal grating component (0 deg is horizontal)
% This component is always parallel to scan lines (y == const) of image.
/Ncycles2  5.0 def	% # of cycles in patch (fractional values OK)
% /Orient2   0.0 def	% Take this as a constant HORIZONTAL component
/Contrast2 0.4 def	% Note:  Cotrast1 + Contrast2 <= 1.0
/Phase2 90 def

% If you need a rectangular or circular frame or border around the patch,
% set Frame to true, and adjust line characteristics of frame.
/Frame false def		% Frame On flag. "false" for no frame
/FrameLineWidth 2.0 def		% line width of frame
/FrameGray 0.0 def		% gray level of frame 0=black, 1=white

% Choose shape: Circular (true) or Square (false)
/Circular true def		% circular patch ("Xsize" is the diameter)
				% "false" for rectangular patch

/inch {72 mul} def	% sigh.
/nx 100 def		% Resolution of 2-D image
/ny 100 def
/Xsize 3 inch def	% Patch size (if modified, %%BoundingBox: must be changed)
/Ysize 3 inch def
/Xcenter 4.5 inch def	% Center coordinate of patch
/Ycenter 4.5 inch def

% ================================================================================
% No user serviceable parts below this line.

% PS code execution starts here
newpath
Xcenter Ycenter translate		  % move to center of patch
Orientation rotate			  % rotate the whole patch
Xsize -0.5 mul Ysize -0.5 mul translate	  % move origin to base of "image"
gsave

% make square image of desired withd
Xsize Ysize scale

% number of cells across image


% Drawing within a unit square will be scaled to Xsize Ysize
% Do clipping.
Circular {   % circular clipping
    newpath 0.5 0.5 0.5 0 360 arc
    clip newpath
} {   % rectangular clipping
    newpath 0 0 moveto 1 0 rlineto 0 1 rlineto -1 0 rlineto
    closepath clip newpath
} ifelse

% Init some internal variables
/S nx string def
/period1  nx Ncycles1 div def		% spatial period in # of pixels for V grating
/periodOR1 period1 Orient1 sin div def	% spatial period for orientation Orient1
/period2  ny Ncycles2 div def		% spatial period in # of pixels for H grating
/tanval Orient1 sin Orient1 cos div def		% tan(Orient1)
/y 0 def

% Here's the pixel value compute loop for (nx, ny) points.
nx ny 8 [nx 0 0 ny 0 0] {
    y period2 div dup truncate sub
    360 mul Phase2 add sin
    127.5 mul
    Contrast2 mul /val2 exch def	% save grating component-2 value in val1
    /offset y tanval div dup periodOR1 div floor periodOR1 mul sub def	% offset
    % do a scan line at current y
    0 1 nx 1 sub {
	S exch dup offset sub		% string (index+offset) (index)
        periodOR1 div dup truncate sub	% 0..1 for each cycle (saw tooth)
        360 mul Phase1 add sin		% sin = -1 .. 1
        127.5 mul			% -127 .. 127
        Contrast1 mul			% component-1
	val2 add 128 add cvi
	put
    } for
    /y y 1 add def		% increment y
    S
}
image


% Draw frame if needed
grestore
Frame {
    FrameLineWidth setlinewidth
    FrameGray setgray
    Circular {   % circular frame
        Xsize 2.0 div dup Ysize 2.0 div exch
        0 360 arc closepath stroke
    } {   % rectangular frame
        0 0 moveto Xsize 0 rlineto
        0 Ysize rlineto Xsize neg 0 rlineto closepath
        stroke
    } ifelse     % Circular
} if             % Frame

showpage		% is allowed in EPS

%%Trailer